The isolation of individual colonies of micro-organisms (and in particular bacteria) is an important procedure in many microbiological laboratories. Traditionally, this isolation of bacteria has been performed manually by skilled laboratory technicians who first dispense a microbiological sample onto the surface of a solid growth culture medium, such as agar in a Petri dish (which will hereafter simply be referred to as a “medium” in an “agar plate” or simply in a “plate”), followed by the use of a hand-tool to spread the sample across the surface of the medium (called “streaking”).
The hand-tool typically includes a terminal loop to make multiple streaks of increasing dilution of the inoculum across the medium. The streaks of increasing dilution tend to provide, generally towards the tail of the streaks, a number of single cells that allow for the growth of isolated microbiological colonies after incubation. These isolated colonies may then be analysed for colony morphology, and may undergo staining and other procedures which are necessary for determining, for example, the genus, the species and the strain of the previously unidentified organism.
Traditionally, the normal laboratory handling regimes for such solid growth culture media plates sees the plates being stored before inoculation and streaking (hereafter referred to as “processing”), and also after processing, in an inverted orientation. By way of explanation, it is usual for solid growth culture medium plates to be stored upside-down such that their lids are facing downwardly and their bottoms (containing the agar) are stored uppermost. This is done to prevent any condensation that may form inside the lid from falling onto the medium surface, which would occur if the plates were not stored in an inverted orientation, thereby damaging the integrity of the medium and (after processing) the microbiological inoculum.
Inoculation and streaking of the type mentioned above is highly repetitious and in many pathology diagnostic microbiology laboratories is usually conducted in very high volumes, such as in volumes as high as 1,000 to 15,000 plates per day. It is tedious and laborious work that therefore is prone to error and inaccuracies. It is quite obviously work that would lend itself to either partial or full automation.
The literature is replete with suggestions for how best to automate these laboratory functions, yet very few of these suggestions have ever actually found success in a commercial laboratory environment. It therefore appears that the successful enablement of suitable laboratory apparatus has to date, for most, proved elusive.
Three recent suggestions for the automation of these laboratory functions can be found in the following documents; U.S. Pat. No. 4,981,802 (C. Wylie et al) titled “Method and Apparatus for Streaking a Culture Medium”, U.S. Pat. No. 6,617,146 (F. Naccarato et al) titled “Method and Apparatus for Automatically Inoculating Culture Media With Bacterial Specimens From Specimen Containers”, and international patent publication WO2005/071055 (Medvet Science Pty Ltd) titled “Microbial Streaking Device” (licensed to the present applicant).
The Wylie and Naccarato patents describe automated and semi-automated apparatus that utilize re-usable streaking tools similar to the hand streaking tools mentioned above, although only the Naccarato patent suggests that its apparatus is capable of orientating a plate from an inverted orientation prior to processing. In this respect, the Naccarato patent describes placing an inverted plate on a conveyor belt, gripping the (uppermost) bottom portion of the plate, and lifting that bottom portion off the lid and away from the belt with an arm that pivots about a horizontal axis that is adjacent to, and lies in the same plane as, the conveyor belt. This suggestion seems to require the lid to already be loose on the plate and is clearly likely to be imprecise and have a high failure rate. At the very least, it seems to be likely to give rise to a reasonably slow operation.
While the Medvet Science publication describes the use of a new form of streaking tool, being a streaking applicator that includes a line of spaced apart contact surfaces (for contact with the surface of solid growth media), the contact surfaces being resiliently flexibly supported by a common support member, it too does not describe an apparatus capable of orientating a plate from an already inverted orientation.
It is an aim of the present invention to provide both a method and an apparatus capable of orientating a solid growth culture medium plate, such as would be required prior to, and after, inoculation and streaking of that plate in a laboratory. In this respect, and as foreshadowed above, it is also an aim of the present invention for the method and apparatus to find use in laboratory situations other than the inoculation and streaking situations described above. Indeed, in its broadest form, the method and apparatus of the present invention may find use in any laboratory to simply provide an automated process of inverting solid growth culture medium plates, with or without lids, either before or after being loaded with agar, and either before or after storage.
Before turning to a summary of the present invention, it must be appreciated that the above description of the prior art has been provided merely as background to explain the context of the invention. It is not to be taken as an admission that any of the material referred to was published or known, or was a part of the common general knowledge in Australia or elsewhere.
It is also useful to provide an explanation of some of the terms that will be used to define the spatial relationship of the apparatus and various parts thereof. In this respect, spatial references throughout this specification will generally be based upon a plate ultimately being inoculated and streaked in an automated streaking apparatus in an upright orientation, with the surface of the medium in the plate being generally flat and horizontal (having previously been stored in an inverted orientation for the reasons mentioned above).
With this environment as the basis, the apparatus and some parts thereof may then be defined with reference to the “horizontal”, allowing further references to “upper” or “upwardly” and “lower” or “downwardly”, and also to the “vertical”. In this respect, the traditional geometric spatial reference to x,y and z dimensions, and then to the x direction (or axis), the y direction (or axis) and the z direction (or axis), will also be adopted, with the x and y directions lying generally horizontally and the z direction lying generally vertically.
Finally, some aspects of the present invention that may ultimately be claimed in isolation (and not in an in-use environment), may nonetheless be difficult to describe and understand in isolation. Thus, some of the following description does describe the invention and its embodiments in such an in-use environment (for example, in association with an automated streaking apparatus, or with reference to its use with an originally inverted plate). Of course, it must be appreciated that the use of such description, and the use of the abovementioned spatial relationships, to define the present invention, is not to be seen as a limitation and certainly is not to be seen as a limitation only to the in-use environment, unless that intention is clearly stated.